We need third-party extensions that link with the Panda3D libraries to continue to work when shipping them with the optimized libraries that deploy-ng uses. To do this, we need the optimized build not to omit symbols that these extensions might depend on.
See #550. Now that we use the Vista API for condition variables, the only place where the distinction is still relevant is Windows XP, and it's just not worth it for that one corner case.
This uses SRWLock on Vista and above, and uses a hand-rolled implementation on Windows XP that uses Events (and a spinlock, if this is a multi-core system).
Since SRWLocks aren't recursive, ReMutexWin32Impl has been added to implement recursive mutices, using old-fashioned critical sections.
MutexImpl now has a constexpr constructor on all implementations.
This reimplements the spinlock on top of std::atomic_flag, which is guaranteed to be lockless. It also inserts the PAUSE (REP NOP) instruction which is strongly recommended to be placed in busy-wait loops by Intel.
This also includes a recursive spinlock implementation.
The spinlock implementation is disabled by default, but can be enabled by adding the --override MUTEX_SPINLOCK=1 flag to makepanda.
Currently, the WeakPointerTo comparison operators compare the raw pointers, but this is not useful as it may cause a false equality if one weak pointer in the comparison is expired and points to memory that has since been reused.
Instead, we can define a comparison based on the control block pointer, which exists since the new weak pointer implementation in 0bb81a43c9. This is implemented in the owner_before method, matching C++11 std::weak_ptr semantics.
I would now recommend deprecating most comparison operators of WeakPointerTo or redefining them to make more sense, ie. comparing equal if they (once) referred to the same object and not if they simply point to the same memory address. This has not yet been done, though code that uses the comparison operators has been fixed in this commit.
Overloads of std::owner_less have been provided for creating a map or set with Weak(Const)PointerTo keys.
There is a bug in clang versions before 3.2 (including the one shipped with Xcode) that makes it give a "conflicting types" compile error when there is a static constexpr function defined outside the class. The way to work around this is either to remove one of the "static" or "constexpr" keywords, or to simply put the definition inline.
See: https://stackoverflow.com/a/17494592/2135754
I would try and upgrade Xcode to version 5 to see if the problem is fixed, but the buildbot still runs OS X Lion (10.7) and the last version of Xcode that works on Lion is 4.6.3, so it seems easier to just apply these workarounds for now.
This renames acquire/release to lock/unlock in order to be compatible with std::lock_guard and std::unique_lock (which will eventually replace the *MutexHolder classes). It will also allow us to typedef MutexImpl to std::mutex later on.
To access a WeakPointerTo in a thread-safe way, use something like this:
if (auto ptr = weak_ptr.lock()) {
..use ptr as regular PointerTo
}
The new implementation no longer needs a reference to be stored to all weak pointers on the WeakReferenceList; a mere count of weak pointers is sufficient. Therefore, callbacks theoretically no longer require a WeakPointerTo to be constructed.
The WeakPointerTo class is not actually atomic; it could be made so, but I don't believe it's worth it at this time.
I have no idea why this error happens, but it does not seem worth the effort to investigate further, so I'm just reverting the previous change to this file.
This is designed to sanity-check the buildsystem, ensuring that the
expected BUILDING_ macros are defined at the expected time. It
also helps catch cases where the wrong BUILDING_/EXPCL_ macros
are used.
rdb
Mitchell Stokes
Brian Lach
Younguk Kim
Sam Edwards
Psychotropos